Tell us some more! Your answer needs to include more details to help people.You can't post answers that contain an email address.Please enter a valid email address.The email address entered is already associated to an account.Login to postPlease use English characters only.

Related Questions:

Turn off computer and restart and hold down the D button while it boots on. This will bring you into the diagnostic screen. Run the diagnostics to check hardware issues. If nothing comes up reboot normally and check your power profile. It is probably set to shut down or suspend after that time to save power.

Your Imac may be one of those affected by Apples purchase of inferior capacitators from Taiwan. If you are less than 3 years from the purchase date, apple will repair the problem for you for free. Just take the unit to your nearest local Apple Genius or tech. If you are outside of the repair extension guidelines, I have provided a link here which can show you or someone more skilled how to repair the problem. Ordering a new motherboard and power supply will set you back a lot of money, however the following guide and pdf give you step by step instructions on how to ressurrect your dead imac without speding more than $100.00. I was able to repair my imac using this guide and it was worth it to save a $2k computer that was only 3 1/2 years old. Check it out:

the following information (in italics and bold) is taken directly from: http://www.jimwarholic.com/2008/07/how-to-repair-apple-imac-g5.php. (this site is complete with instructions, manual and the full compliment of materials available at an extremely affordable and fair price. I took a chance and repaired my own, it is not as hard as it sounds1)

The iMac G5 Repair Extension Program for Video and Power Issues applies to first generation iMac G5 computers that have video or power-related issues as a result of a specific component failure. If your iMac G5 is exhibiting any of the symptoms listed below and your computer's serial number is within the noted ranges, your computer may be eligible for repair, free of charge. If Apple or an Apple Authorized Service Provider (AASP) determines that your iMac G5 computer is eligible as part of the program, the repair will be covered by Apple for up to three years from the original date of purchase even if your iMac G5 is out of warranty.

This is a worldwide Apple program.Affected systems will exhibit one of the following video- or power-related symptoms:Scrambled or distorted video No video No power Note: If your iMac G5 is not experiencing any of these symptoms, you do not have to contact Apple or any Apple Authorized Service Provider.

Which iMac G5 computers are affected by the iMac G5 Repair Extension Program for Video and Power Issues? The program is available for certain first generation iMac G5 models that were sold between approximately September 2004 and June 2005 featuring 17- and 20-inch displays with 1.6GHz and 1.8GHz G5 processors.

The affected iMac G5 computers have serial numbers where the first 5 digits fall into the ranges noted below.

Serial Number ranges:W8435xxxxxx - W8522xxxxxx QP435xxxxxx - QP522xxxxxx CK435xxxxxx - CK522xxxxxx YD435xxxxxx - YD522xxxxxx Some second generation iMac G5 computers have serial numbers that fall within the upper band of the ranges listed below. Only first generation iMac G5 computers are affected by this program.Where do I find the serial number of my iMac G5?The 11-digit serial number is located on a label under the foot of the iMac G5. There is a bar code underneath the serial number.To view the label, hold the sides of the iMac and gently lay the computer face down on a soft, clean towel or cloth.

Is the iMac G5 Repair Extension program available for other Apple computers?

This program applies only to the systems noted in this FAQ. Other versions of the iMac G5 line are not part of this program. Click here for more information on how to identify iMac G5 models

Free guide for how to repair the motherboard capacitors, rescue the hard drive and more.

It sounds like there's underlying problems unrelated to Panther. If the computer boots from the the old HD, but then the HD didn't show under Disk Utility, this is an intermittent problem.
Try replacing the cable that goes to the HD (if there is one), it may have become damaged sufficiently that things aren't working under "heavy use" (like trying to install an OS). If there is no cable, or replacing it doesn't work, I'd suggest putting the original HD in and selling the computer as-is.
Again, if it still botos from the old HD, then it's not a problem with the HD or Panther, unless the reconditioned HD you bought was faulty (unlikely but possible). More likely is when you installed the reconditioned HD, something else changes (e.g. connection made better contact) that caused the HD to show.